@Irish Maeve
I found a good way to lower Blood Glucose if it was high - certainly when I was in the teens like you've been today - was a gentle stroll for at least 20 minutes.
I noticed mention of a brisk walk - I'd suggest avoiding that for the full duration as your body may do a liver dump and actually raise your Blood Glucose levels.
There's something to be said for gentle walk interspersed with short periods of brisk walking but, for now I'd suggest it's better to take a long slow stroll to burn the glucose.
I found 30 minutes strolling would bring my blood glucose down by around 3 - 4 mmol / L you will probably have different results.